The present invention relates generally to systems for electromagnetically actuating engine valves. More specifically, it relates to the control of the actuator armature and engine valve with soft seating of actuator armature to actuator cores, and soft seating of engine valves.
It has been well known that variable valve timing for internal combustion engines will improve their fuel economy and reduce emissions. An electromagnetic valve actuation system (EMVAS) is one of the technologies to realize the required variable valve timing.
One form of known electromechanical actuators includes an armature that moves back and forth along a linear travel path between two electromagnet cores. The armature functions as an actuating member and is operated against the force of two springs positioned on opposite sides of the armature. In an unactuated state, the armature is positioned midway between the two cores by the opposing springs.
Electromagnetic actuators of the above-described type are used, for example, for operating cylinder valves of internal combustion engines. Each cylinder valve is actuated by the armature of the associated electromagnetic actuator. The armature which, by virtue of the forces of the return springs, assumes its position of rest between the two electromagnets, is alternatingly attracted by the one or the other electromagnet, and, accordingly, the cylinder valve is maintained in its closed or open position.
A first problem associated with EMVAS""s is to initialize the armature from a middle position to either a valve open position or a valve closed position with soft seating of the armature and the engine valve.
A second problem associated with EMVAS""s is to control the armature transition from the open position to the closed position or from the closed position to the open position with soft seating between the armature cores and the armature, and between the valve and the engine head.
A third problem is the robustness of the soft seating initialization and transition control.
A fourth problem is the high-bandwidth and complicated current shaping requirement for achieving the required soft seating control.
A fifth problem is the power consumption minimization of the EMVAS and the power requirement reduction to minimize the system size, weight and cost.
A sixth problem is the power wasted every time the EMVAS and the valve train are shut down.
The present invention concerns an apparatus and method for operating an electromagnetic valve actuator coil in a manner to solve the above-described problems by using an energy feedback and loss compensation algorithm. The apparatus controls a valve actuator having an armature positioned between open and close coils. Included is a position processor that generates an energy signal and open and close timer signals in response to a position signal representing a position of the valve actuator armature relative to the open and close coils. A current controller generates a final current command signal and a normalized energy signal in response to the energy signal and an event generator generates event signals in response to the open and close timer signals and the normalized energy signal. A supervision logic controller generates initialization and transition signals in response to the final current command signal and the event signals, the initialization and transition signals defining current pulse magnitude and duration for soft seating of the armature on a seating surface of cores associated with the open and close coils.
The method for controlling includes the steps of: generating a final current command signal in response to a position signal representing a position of a valve actuator armature relative to open and close coils; generating a first signal in response to the final current command signal defining a higher magnitude current pulse of predetermined duration to draw the armature toward the one of the coils; generating a second signal in response to the final current command signal defining a predetermined period of no current pulse; and generating a third signal in response to the final current command signal defining a lower magnitude holding current pulse for soft seating of the armature on a seating surface of a core associated with the one coil.